add support for applying custom comp_op and opacity when blending map background image into background color at render time - refs mapnik/mapnik-support#8
Additional optional dependency on librasterlite
always link libdl on linux - needed on some systems after #1804 - closes #1998
Merge pull request #1997 from kapouer/patch-1

Additional optional dependency on librasterlite
Merge branch 'master' into c++11
+ geometry::types Exterior/Interior polygon loops
further develop 2.3.0 changelog
more changelog additions
more 2.3.x changelog updates
Merge pull request #1966 from mapnik/background-image-comp-op

Map background-image-comp-op and background-image-opacity
add mention of background-image-opacity and background-image-comp-op to changelog - refs #1966
Merge branch 'master' of github.com:mapnik/mapnik
Merge branch 'master' into c++11
Merge branch 'geometry-types' into c++11